Method for producing a polychloroprene latex

ABSTRACT

A method for producing a polychloroprene latex, which comprises copolymerizing chloroprene and an ethylenically unsaturated carboxylic acid in the presence of a polyvinyl alcohol, wherein a glycol ether is also present during the copolymerization.

This application is a Continuation Ser. No. 08/325,079, filed on Oct.19, 1994, now abandoned.

The present invention relates to a method for producing apolychloroprene latex useful as an adhesive. More particularly, itrelates to a method for producing a polychloroprene latex which isexcellent in the contact property (initial adhesive strength), waterresistance, etc. and which is suitable for use as an aqueouscontact-adhesive.

Heretofore, adhesives using polychloroprene as the base material weremainly of a solvent type. However, in recent years, solvent typeadhesives have been disfavored in view of such problems as the toxicity,the danger of fire and the environmental pollution by the organicsolvents during their production or use, and demand for non-solvent typeadhesives has been increasing.

A polychloroprene latex adhesive has good adhesive properties and isfree from the above problems, since it requires no organic solvent suchas toluene or hexane during its production. Accordingly, it is expectedto be a substitute for conventional solvent-type adhesives.

Such a polychloroprene latex adhesive is coated on both objects to bebonded, and the resulting adhesive layers will then be substantiallydried and then bonded to each other, whereby it provides a high initialadhesive strength immediately after the bonding.

By virtue of such a feature, the adhesive of this type is practicallyused as an aqueous contact-adhesive. As the range of its applicationexpands, improvement of the adhesive properties such as the contactproperty and water resistance has been increasingly demanded.

Japanese Unexamined Patent Publication No. 22047/1975 and EP 0451998 A2disclose latexes obtained by polymerizing chloroprene and an unsaturatedcarboxylic acid in the presence of a polyvinyl alcohol. However, latexesprepared in accordance with Examples given in these publications, arenot necessarily satisfactory with respect to their water resistantadhesive strength.

The water resistance of the product bonded by a latex adhesive usuallydecreases by the presence of a hydrophilic material such as anemulsifier contained in the latex. In the above case, it is known thatthe decrease of the water resistance can be controlled by reducing theamount of the polyvinyl alcohol incorporated during the production ofthe latex. However, in the above-mentioned method, it tends to bedifficult to produce a stable latex if the amount of polyvinyl alcoholis reduced, and it has been difficult to obtain a latex satisfying boththe stability and the water resistance.

It is an object of the present invention to solve such problems of theprior art and to provide a method for producing a polychloroprene latexwhich is excellent in the contact property and the water resistantadhesive strength, while securing the stability of the latex.

The present inventors have found it possible to improve the contactproperty and the water resistant adhesive strength of a polychloroprenelatex adhesive, while securing the stability of the latex, by conductingpolymerization in the co-existence of a certain specific compound duringthe production of a polychloroprene latex.

That is, the present invention provides (1) a method for producing apolychloroprene latex, which comprises copolymerizing chloroprene and anethylenically unsaturated carboxylic acid in the presence of a polyvinylalcohol, wherein a glycol ether is also present during thecopolymerization.

More specifically, it provides (2) the method for producing apolychloroprene latex according to (1), wherein from 0.5 to 10 parts byweight of the ethylenically unsaturated carboxylic acid, from 0.5 to 10parts by weight of the polyvinyl alcohol and from 0.5 to 15 parts byweight of the glycol ether are present per 100 parts by weight of thechloroprene, (3) the above-mentioned method for producing apolychloroprene latex, wherein the ethylenically unsaturated carboxylicacid is methacrylic acid, the polyvinyl alcohol has an average degree ofpolymerization of from 200 to 3,000 and a saponification degree of atleast 70 mol %, and the glycol ether is a glycol monoether and/or aglycol diether, and (4) the above-mentioned method for producing apolychloroprene latex, wherein the glycol monoether is at least onemember selected from the group consisting of3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol and ethylene glycolmonobutyl ether, and the glycol diether is at least one member selectedfrom the group consisting of ethylene glycol dimethyl ether, ethyleneglycol dibutyl ether and triethylene glycol dibutyl ether. Further, thepresent invention provides (5) the above-mentioned method for producinga polychloroprene latex, wherein the chloroprene contains at mostequimolar amount of 2,3-dichlorobutadiene.

Now, the present invention will be described in detail.

In the present invention, as the main material, chloroprene or a mixtureof chloroprene with other monomer copolymerizable with chloroprene(hereinafter referred to as "a mixture of chloroprene with a monomer"),is employed.

Said other monomer may be any monomer so long as it is copolymerizablewith chloroprene. For example, 1,3-butadiene, isoprene,2,3-dichlorobutadiene or styrene may be mentioned. These monomers may beused alone or in combination as a mixture of two or more of them.

When a mixture of chloroprene with a monomer is used, the content of themonomer other than chloroprene is preferably within a range not toimpair the physical properties of the polychloroprene, for example, atmost equimolar amount to the chloroprene.

In the present invention, specific examples of the ethylenicallyunsaturated carboxylic acid include acrylic acid, methacrylic acid,crotonic acid, fumaric acid, maleic acid, citraconic acid and glutaconicacid. These acids may be used alone or in combination as a mixture oftwo or more of them.

The amount of the ethylenically unsaturated carboxylic acid variesdepending upon the type or the molecular weight of the unsaturatedcarboxylic acid, but it is preferably from 0.5 to 10 parts by weight,more preferably from 1 to 5 parts by weight, per 100 parts by weight ofthe chloroprene or the mixture of chloroprene with a monomer. If theamount of the ethylenically unsaturated carboxylic acid is less than 0.5part by weight, no adequate adhesive strength or heat resistant strengthtends to be obtained. On the other hand, if it exceeds 10 parts byweight, the stability tends to be low during the storage or blending ofthe latex.

In the present invention, as the glycol ether, a glycol monoether or aglycol diether may, for example, be mentioned. Examples of the glycolmonoether in the present invention include ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,diethylene glycol monomethyl ether, diethylene glycol monobutyl ether,propylene glycol monomethyl ether, propylene glycol monobutyl ether,ethylene glycol mono-tert-butyl ether, 3-methoxy-1-butanol and3-methyl-3-methoxy-1-butanol.

Examples of the glycol diether in the present invention include ethyleneglycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycoldimethyl ether, diethylene glycol diethyl ether, triethylene glycoldimethyl ether, triethylene glycol diethyl ether, propylene glycoldimethyl ether and propylene glycol dibutyl ether.

These glycol ethers may be used alone or in combination as a mixture oftwo or more of them.

The amount of the glycol ether is usually from 0.5 to 15 parts byweight, preferably from 2.0 to 10 parts by weight, per 100 parts byweight of the chloroprene or the mixture of chloroprene with a monomer.If the amount is less than 0.5 part by weight or more than 15 parts byweight, the contact property and the water resistance tend to be poor.

In the present invention, as the polyvinyl alcohol, one commonly used,may be employed, such as a polyvinyl alcohol having an average degree ofpolymerization of from 200 to 3,000 and a saponification degree of atleast 70 mol %. Otherwise, the one copolymerized with other monomer suchas acrylamide or maleic anhydride, or the one having a part of apolyvinyl alcohol chemically modified by carboxylation or sulfonation,may also be used.

The amount of the polyvinyl alcohol is usually from 0.5 to 10 parts byweight, preferably from 1 to 5 parts by weight, per 100 parts by weightof the chloroprene or the mixture of chloroprene with a monomer. If theamount of the polyvinyl alcohol is less than 0.5 part by weight, theemulsifying power tends to be inadequate, and formation of aggregatestends to occur frequently during the polymerization reaction. On theother hand, if it exceeds 10 parts by weight, the viscosity tends toincrease during the polymerization reaction, whereby stirring will behindered, or abnormal heat generation is likely to take place, wherebyit will be difficult to conduct the polymerization under a stabilizedcondition, and further, the water resistance tends to be low.

The amount of the polyvinyl alcohol is very much related to the amountof the glycol ether. Namely, the glycol ether itself also has anemulsifying power. Therefore, in a system where the glycol ether is usedin a large amount, the emulsion stability can be maintained with a smallamount of the polyvinyl alcohol. And, in such a case, there will be animproved effect for the water resistant adhesive property due to thereduced amount of the polyvinyl alcohol. On the other hand, in a systemwhere the glycol ether is used in a small amount, it is not proper tominimize the amount of the polyvinyl alcohol to maintain the emulsionstability.

The method of the present invention may be carried out, for example, byadding to an aqueous solution of a polyvinyl alcohol, chloroprene or amixture of chloroprene with a monomer, an ethylenically unsaturatedcarboxylic acid, a glycol ether as well as a molecular weightcontrolling agent (a chain transfer agent of various types), apolymerization initiator, etc., and stirring the resulting mixture whilemaintaining it at a constant temperature to conduct emulsionpolymerization under an inert atmosphere to obtain a polychloroprenelatex. Further, a pH controlling agent may be present in thepolymerization system, as the case requires.

To the polychloroprene latex obtained by the present invention, asurfactant such as a fatty acid alkanolamide, or a resin emulsion whichis commonly used, may be added. A typical example of such a resinemulsion is the one having a rosin-type resin (resin derived from rosinether, hydrogenated rosin or polymerized rosin), a terpene-type resin, aphenol-type resin, a cumarone-indene resin, an aliphatic hydrocarbonresin or an aromatic petroleum-type resin dispersed in water by means ofan anionic or nonionic emulsifier or dispersant. Such a resin emulsionmay be the one having a single resin dispersed in water or the onehaving a plurality of resins dispersed in water.

Further, to the polychloroprene latex obtained by the present invention,additives commonly used for latexes, such as an antioxidant, afilm-forming agent, a metal oxide, a vulcanizer and a thickener, mayoptionally be incorporated. Such additives may be blended by means ofany one of mixing machines which are commonly used for blending latexes.

The polychloroprene latex obtained by the present invention is suitablefor use as an adhesive for bonding objects of the same type or differenttypes such as papers, woods, cloths, leathers, rubbers, plastics,plastic foams, porcelains, glasses, ceramics and metals.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

EXAMPLE 1

Into a 3 l four-necked flask, 40 parts by weight of a polyvinyl alcohol(Denka Poval B-05, average degree of polymerization: 550, saponificationdegree: 88%) and 950 parts by weight of pure water were introduced,heated (60° C.) and dissolved. This aqueous solution was cooled to aboutroom temperature, then 970 parts by weight of chloroprene, 30 parts byweight of methacrylic acid, 25 parts by weight of3-methyl-3-methoxy-1-butanol and 3 parts by weight of octyl mercaptanwere added thereto.

This mixture was stirred (200 rpm) while maintaining it at 40° C., andan initiator (potassium persulfate/sodium anthraquinone-β-sulfonate) wasadded under a nitrogen stream to conduct polymerization to obtain alatex.

Then, a 20% diethanolamine aqueous solution was added in a proper amountthereto to adjust the pH to 7. Then, 30 parts by weight of an aqueoussolution containing 20% by weight of a 1:2 mol type fatty acidalkanolamide (MODICOL N, manufactured by Diamond Shamrock Chemical Co.)was added thereto to obtain a polychloroprene latex of the presentinvention.

Then, with respect to this polychloroprene latex, the adhesiveproperties were evaluated by the following methods.

(1) Contact property (canvas/canvas)

On two sheets of canvas (cotton cloth having a length of 14 cm and awidth of 2.5 cm), the latex was coated twice so that the total coatedamount would be 350 g/m² (wet amount). In the first coating, one half ofthe predetermined amount was coated and then heated for 5 minutes in aGeer oven of 70° C. for drying, and in the second coating, the rest ofthe adhesive was coated, and this was again heated for 5 minutes in aGeer oven of 70° C. for drying. The coated sheets were taken out at roomtemperature and immediately bonded to each other by pressing them with ahand roller. Immediately after the bonding, they were peeled at apeeling speed of 100 mm/min, whereby an average value of the tensileloads was taken as the contact property (the initial adhesive strength).

(2) Contact property (veneer/veneer)

In the same manner, the polychloroprene latex was coated on two sheetsof veneer and dried. Then, the coated sheets were bonded by applying apressure of about 10 kg/cm² for about 30 seconds, and immediatelythereafter, they were manually peeled, whereby the adhesive force wasevaluated by five ratings (5 point: best, 4 point: good, 3 point: fair,2 point: poor, 1 point: very poor). Further, the effective bond area atthat time was visually evaluated.

(3) Adhesive strength (canvas/canvas)

A test specimen bonded as in (1) was aged at 23° C. for 7 days and thenpeeled at a peeling speed of 100 mm/min, whereby an average value of thetensile loads was taken as the adhesive strength.

(4) Water resistant adhesive strength (canvas/canvas)

A test specimen bonded as in (1) was aged at 23° C. for 7 days andfurther immersed in water for 2 days, and then it was peeled at apeeling speed of 100 mm/min, whereby an average value of the tensileloads was taken as the water resistant adhesive strength.

(5) Heat resistant creep (canvas/canvas)

At one end of the test specimen bonded as in (1), 200 g of a weight wasattached, and the other end was secured at a ceiling, and the time untilthe canvas to which the weight was attached, was peeled and dropped inan atmosphere of 70° C. at 180° peeling, was measured.

EXAMPLE 2

A polychloroprene latex was prepared in the same manner as in Example 1except that 200 parts by weight of chloroprene out of 970 parts byweight was replaced by 2,3-dichlorobutadiene, and the adhesiveproperties were evaluated.

EXAMPLE 3

A polychloroprene latex was prepared in the same manner as in Example 1except that the amount of 3-methyl-3-methoxy-1-butanol was changed to 50parts by weight, and the amount of the polyvinyl alcohol was changed to35 parts by weight, and the adhesive properties were evaluated.

EXAMPLE 4

A polychloroprene latex was prepared in the same manner as in Example 1except that the amount of 3-methyl-3-methoxy-1-butanol was changed to 50parts by weight, and the amount of the polyvinyl alcohol was changed to30 parts by weight, and the adhesive properties were evaluated.

EXAMPLE 5

A polychloroprene latex was prepared in the same manner as in Example 1except that the amount of 3-methyl-3-methoxy-1-butanol was changed to 25parts by weight, and the amount of the polyvinyl alcohol was changed to25 parts by weight, and the adhesive properties were evaluated.

EXAMPLE 6

A polychloroprene latex was prepared in the same manner as in Example 1except that the amount of 3-methyl-3-methoxy-1-butanol was changed to 25parts by weight, and the amount of the polyvinyl alcohol was changed to20 parts by weight, and the adhesive properties were evaluated.

EXAMPLE 7

A polychloroprene latex was prepared in the same manner as in Example 1except that instead of 3-methyl-3-methoxy-1-butanol, the same amount of3-methoxy-1-butanol was added, and the adhesive properties wereevaluated.

EXAMPLE 8

A polychloroprene latex was prepared in the same manner as in Example 1except that instead of 3-methyl-3-methoxy-1-butanol, the same amount ofethylene glycol monobutyl ether was added, and the adhesive propertieswere evaluated.

EXAMPLE 9

A polychloroprene latex was prepared in the same manner as in Example 1except that instead of 3-methyl-3-methoxy-1-butanol, the same amount ofethylene glycol dimethyl ether was added, and the adhesive propertieswere evaluated.

EXAMPLE 10

A polychloroprene latex was prepared in the same manner as in Example 1except that instead of 3-methyl-3-methoxy-1-butanol, the same amount ofethylene glycol dibutyl ether was added, and the adhesive propertieswere evaluated.

EXAMPLE 11

A polychloroprene latex was prepared in the same manner as in Example 1except that instead of 3-methyl-3-methoxy-1-butanol, the same amount oftriethylene glycol dimethyl ether was added, and the adhesive propertieswere evaluated.

COMPARATIVE EXAMPLE 1

A polychloroprene latex was prepared in the same manner as in Example 1except that no 3-methyl-3-methoxy-1-butanol was added, and the adhesiveproperties were evaluated.

COMPARATIVE EXAMPLE 2

Emulsion polymerization was carried out in the same manner as inComparative Example 1 except that the amount of the polyvinyl alcoholwas changed to 20 parts by weight. However, the emulsification was poor,and aggregates precipitated during the polymerization.

COMPARATIVE EXAMPLE 3

A polychloroprene latex was prepared in the same manner as inComparative Example 1 except that the amount of the polyvinyl alcoholwas changed to 50 parts by weight, and the adhesive properties wereevaluated.

The results of the above Examples 1 to 5 are shown in Table 1, theresults of Examples 6 to 10 are shown in Table 2, and the results ofExample 11 and Comparative Examples 1 to 3 are shown in Table 3.

                  TABLE 1                                                         ______________________________________                                                   Exam- Exam-   Exam-   Exam- Exam-                                             ple 1 ple 2   ple 3   ple 4 ple 5                                  ______________________________________                                        Formulation for                                                               polymerization                                                                Chloroprene  970     770     970   970   970                                  2,3-Dichlorobutadiene                                                                      --      200     --    --    --                                   Methacrylic acid                                                                            30      30      30    30    30                                  Octyl mercaptan                                                                             3       3       3     3     3                                   Polyvinyl alcohol.sup.1)                                                                    40      40      35    30    25                                  Pure water   950     950     950   950   950                                  3-Methyl-3-methoxy-1-                                                                       25      25      50    50    25                                  butanol.sup.2)                                                                3-Methoxy-1-butanol                                                                        --      --      --    --    --                                   Ethylene glycol                                                                            --      --      --    --    --                                   monobutyl ether                                                               Ethylene glycol dimethyl                                                                   --      --      --    --    --                                   ether                                                                         Ethylene glycol dibutyl                                                                    --      --      --    --    --                                   ether                                                                         Triethylene glycol                                                                         --      --      --    --    --                                   dibutyl ether                                                                 Physical properties of the                                                    latex                                                                         Specific gravity                                                                           1.095   1.098   1.089 1.098 1.089                                Mechanical stability                                                                       0.0055  0.0056  0.0082                                                                              0.0080                                                                              0.0026                               (%).sup.3)                                                                    Particle size (mm).sup.4)                                                                  199     202     210   259   327                                  Contact property (initial                                                                  1.10    1.20    1.22  1.87  1.70                                 adhesion).sup.5)                                                              (canvas/canvas) (kg/cm)                                                       Contact property (initial                                                                  5 point 5 point 5 point                                                                             5 point                                                                             5 point                              adhesion).sup.6)                                                                           (100%)  (100%)  (100%)                                                                              (100%)                                                                              (100%)                               (veneer/veneer) 5 ratings                                                     Adhesive strength.sup.7)                                                                   2.6     4.1     2.2   2.8   2.3                                  (canvas/canvas) (kg/cm)                                                       Water resistant adhesive                                                                   0.33    0.35    0.99  1.28  1.36                                 strength.sup.8)                                                               (canvas/canvas) (kg/cm)                                                       Heat resistant creep.sup.9)                                                                at least                                                                              at least                                                                              at least                                                                            at least                                                                            at least                             (Drop time)   60      60      60    60    60                                  (canvas/canvas) (min)                                                         ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                   Exam- Exam-   Exam-   Exam- Exam-                                             ple 6 ple 7   ple 8   ple 9 ple 10                                 ______________________________________                                        Formulation for                                                               polymerization                                                                Chloroprene  970     970     970   970   970                                  2,3-Dichlorobutadiene                                                                      --      --      --    --    --                                   Methacrylic acid                                                                            30      30      30    30    30                                  Octyl mercaptan                                                                             3       3       3     3     3                                   Polyvinyl alcohol.sup.1)                                                                    20      40      40    40    40                                  Pure water   950     950     950   950   950                                  3-Methyl-3-methoxy-1-                                                                       25     --      --    --    --                                   butanol.sup.2)                                                                3-Methoxy-1-butanol                                                                        --       25     --    --    --                                   Ethylene glycol                                                                            --      --       25   --    --                                   monobutyl ether                                                               Ethylene glycol dimethyl                                                                   --      --      --     25   --                                   ether                                                                         Ethylene glycol dibutyl                                                                    --      --      --    --     25                                  ether                                                                         Triethylene glycol                                                                         --      --      --    --    --                                   dibutyl ether                                                                 Physical properties of the                                                    latex                                                                         Specific gravity                                                                           1.098   1.096   1.095 1.096 1.096                                Mechanical stability                                                                       0.0097  0.0093  0.0060                                                                              0.0030                                                                              0.0085                               (%).sup.3)                                                                    Particle size (mm).sup.4)                                                                  389     201     209   202   208                                  Contact property (initial                                                                  1.69    1.20    1.25  1.80  2.30                                 adhesion).sup.5)                                                              (canvas/canvas) (kg/cm)                                                       Contact property (initial                                                                  5 point 5 point 5 point                                                                             5 point                                                                             5 point                              adhesion).sup.6)                                                                           (100%)  (100%)  (100%)                                                                              (100%)                                                                              (100%)                               (veneer/veneer) 5 ratings                                                     Adhesive strength.sup.7)                                                                   2.2     2.8     2.8   3.6   3.9                                  (canvas/canvas) (kg/cm)                                                       Water resistant adhesive                                                                   1.08    0.32    0.33  1.48  1.85                                 strength.sup.8)                                                               (canvas/canvas) (kg/cm)                                                       Heat resistant creep.sup.9)                                                                at least                                                                              at least                                                                              at least                                                                            at least                                                                            at least                             (Drop time)   60      60      60    60    60                                  (canvas/canvas) (min)                                                         ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                          Compar-  Compar-  Compar-                                              Example                                                                              ative    ative    ative                                                11     Example 1                                                                              Example 2                                                                              Example 3                                 ______________________________________                                        Formulation for                                                               polymerization                                                                Chloroprene  970      970      970    970                                     2,3-Dichlorobutadiene                                                                      --       --       --     --                                      Methacrylic acid                                                                            30       30       30     30                                     Octyl mercaptan                                                                             3        3        3      3                                      Polyvinyl alcohol.sup.1)                                                                    40       40       20     50                                     Pure water   950      950      950    950                                     3-Methyl-3-methoxy-1-                                                                      --       --       --     --                                      butanol.sup.2)                                                                3-Methoxy-1-butanol                                                                        --       --       --     --                                      Ethylene glycol                                                                            --       --       --     --                                      monobutyl ether                                                               Ethylene glycol dimethyl                                                                   --       --       --     --                                      ether                                                                         Ethylene glycol dibutyl                                                                    --       --       --     --                                      ether                                                                         Triethylene glycol                                                                          25      --       --     --                                      dibutyl ether                                                                 Physical properties of the                                                    latex                                                                         Specific gravity                                                                           1.097    1.094    Stable 1.096                                   Mechanical stability                                                                       0.0062   0.0056   polymeri-                                                                            0.0020                                  (%).sup.3)                     zation                                         Particle size (mm).sup.4)                                                                  196      217      impossible                                                                           140                                     Contact property (initial                                                                  1.10     1.06     --     1.00                                    adhesion).sup.5                                                               (canvas/canvas) (kg/cm)                                                       Contact property (initial                                                                  5 point  3 point  --     2 point                                 adhesion).sup.6)                                                                           (100%)   (30%)           (10%)                                   (veneer/veneer) 5 ratings                                                     Adhesive strength.sup.7)                                                                   3.2      2.4      --     2.4                                     (canvas/canvas) (kg/cm)                                                       Water resistant adhesive                                                                   1.82     0.27     --      0                                      strength.sup.8)                                                               (canvas/canvas) (kg/cm)                                                       Heat resistant creep.sup.9)                                                                at least 36       --     40                                      (Drop time)  60                                                               (canvas/canvas) (min)                                                         ______________________________________                                    

Notes in the Tables

1) Polyvinyl alcohol: Denka-Poval B-05 (average degree ofpolymerization: 550, saponification degree: 88%)

2) 3-Methyl-3-methoxy-1-butanol: SOLFIT (KURARAY Co., Ltd.)

3) Mechanical stability: Maron type stability tester (10 kg, 1000 rpm,10 min)

4) Particle size: particle size measuring apparatus (Sub-micron ParticleAnalyzer model 4/COULTER ELECTRONICS.)

5) Contact property (canvas/canvas): coated amount: 350 g/m² (wetamount, coated twice with a half amount each time), open time: 70° C., 5min, bonding: press bonding by a hand roller, measurement of theadhesive force: immediately after the bonding, the peeling load at apeeling speed of 100 mm/min was measured.

6) Contact property (veneer/veneer): coated amount: 200 g/m² (wetamount, the total amount was coated all at once), open time: 70° C., 5min, bonding: press bonded under a pressure of about 10 kg/m².Immediately after the bonding, the bonded test specimen was manuallypeeled, whereby the adhesive force was evaluated by five ratings.Further, the proportion of the effective adhesive area of the adhesivefailure surface was visually measured and shown in a bracket.

7) Adhesive strength (canvas/canvas): coated amount: 350 g/m² (wetamount, coated twice with a half amount each time), open time: 70° C.,10 min, bonding: press bonding by a hand roller, measurement of theadhesive force: upon expiration of 7 days (23° C., 50 RH %) after thebonding, the peeling load at a peeling speed of 100 mm/min was measured.

8) Water resistant adhesive strength (canvas/canvas): the test specimenas in 7) was further immersed in water for 2 days, whereupon the peelingload was measured.

9) Heat resistant creep (canvas/canvas): the same test specimen as usedfor the measurement of the adhesive strength was employed. At one end ofthis bonded test specimen, a weight of 200 g was attached and suspendedin an atmosphere of 70° C., whereby the time until the weight dropped,was measured.

What is claimed is:
 1. A method for producing a polychloroprene latexwhich consists essentially of:copolymerizing chloroprene and at leastone ethylenically unsaturated carboxylic acid in the presence of apolyvinyl alcohol and glycol ether, wherein from 0.5 to 10 parts byweight of the ethylenically unsaturated carboxylic acid, from 0.5 to 10parts by weight of the polyvinyl alcohol and from 0.5 to less than 10parts by weight of the glycol ether are present in the reaction mediumper 100 parts by weight of the chloroprene, thereby preparing said latexwhich can be directly applied as an adhesive to a substrate.
 2. A methodfor producing a polychloroprene latex, which consists essentiallyof:copolymerizing chloroprene and at least one ethylenically unsaturatedcarboxylic acid in the present of a polyvinyl alcohol and a glycolether, wherein from 0.5 to 10 parts by weight of the ethylenicallyunsaturated carboxylic acid selected from the group consisting ofacrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleicacid, citraconic acid and glutaconic acid, from 0.5 to 10 parts byweight of the polyvinyl alcohol and from 0.5 to less than 10 parts byweight of the glycol ether are present in the reaction medium per 100parts by weight of the chloroprene, thereby preparing said latex whichcan be directly applied as an adhesive to a substrate.
 3. The method forproducing a polychloroprene latex according to claim 1, wherein theethylenically unsaturated carboxylic acid is at least one memberselected from the group consisting of acrylic acid, methacrylic acid,crotonic acid, fumaric acid, maleic acid, citraconic acid and glutaconicacid.
 4. The method for producing a polychloroprene latex according toclaim 1, wherein the ethylenically unsaturated carboxylic acid ismethacrylic acid.
 5. The method for producing a polychloroprene latexaccording to claim 1, wherein the polyvinyl alcohol has an averagedegree of polymerization of from 200 to 3,000 and a saponificationdegree of at least 70 mol %.
 6. The method for producing apolychloroprene latex according to claim 1, wherein the glycol ether isa glycol monoether.
 7. The method for producing a polychloroprene latexaccording to claim 6, wherein the glycol monoether is at least onemember selected from the group consisting of3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, ethylene glycolmonobutyl ether and ethylene glycol mono-tert-butyl ether.
 8. The methodfor producing a polychloroprene latex according to claim 1, wherein theglycol ether is a glycol diether.
 9. The method for producing apolychloroprene latex according to claim 8, wherein the glycol dietheris at least one member selected from the group consisting of ethyleneglycol dimethyl ether, ethylene glycol dibutyl ether and triethyleneglycol dibutyl ether.
 10. The method for producing a polychloroprenelatex according to claim 1, wherein the chloroprene contains at mostequimolar amount of 2,3-dichlorobutadiene.